Achievements
Complete the following achievements to unlock Xbox Live Gamerscore points:

Lock 'n' Load (25) - Found rifle.
Sightseeing (10) - Found one photo.
Josh's Gallery (50) - Found all photos.
Alchemilla's Finest (10) - Defeated one Nurse.
Eddie's Legacy (10) - Defeated one Feral.
Lurk No More (10) - Defeated one Lurker.
To The Point (10) - Defeated one Needler.
Split Personality (10) - Defeated one Schism.
Shades of James (20) - Defeated one Siam.
Clear the Air (10) - Defeated one Smog.
Creeper Reaper (10) - Defeated one Swarm.
Out of Order (10) - Defeated one Order member.
Kaufmann's Handiwork (10) - Found one serum.
Health Junkie (50) - Found all serums.
The Old Gods... Haven't Left This Place (100) - Complete game on hard difficulty.
Nursery Rhymes (50) - Found all the children's drawings.

Unlock Extra Weapons
Beat the game once to unlock Circular Saw (can be found in the garage at the Shepard's family home) and Laser Pistol (can be found in Joshua's room, on top of his foot locker).

Easy "The Old Gods..." Achievement
View The "UFO" ending under the Normal difficulty to unlock the laser pistol. After saving the game, start it again under the Hard difficulty setting. When you finally reach the house and go into Alex's/Josh's room, you will see the laser pistol next to the bed. With unlimited ammunition and extreme power, the rest of the game will be very easy.

Glitch: Stuck in A Corner
It is possible to become stuck in a corner that contains two nearby objects. You can become trapped in the triangular space between the objects and the corner. To exit from such a location, take out your gun and walk forward or forward diagonally.